in reply to reading binary data from a file

push 
my $fn = @ARGV[0];

open(my $fh, '<', $fn)
    or die("Can't open \"$fn\": $!\n");

binmode($fh);

my @recs;
while (read($fh, my $rec, 158)) {
    push @recs, $rec;
}

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Don't forget binmode on binary files!

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Re^2: reading binary data from a file
by amigero (Novice) on Oct 29, 2009 at 00:12 UTC
    Thank you.

    Now, how do I access the 23rd to 35th byte for every row and put it into another array? In Matlab it would be:
     new_array = array(:,23:35);
    and you're done

    Second, how do I access a row and column in that array and put it into a scalar? In Matlab it would be:
     scalar = array(3,4)
    meaning I'm grabing the 3rd row and 4th column byte.
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      substr can be used to extract portions of other strings. It returns a string, though. If you want to treat each character of that string as a byte, you can then use unpack 'C*'.

      Square brackets can be used to create anonymous arrays. The contents of the brackets are assigned to the array. The operator returns a reference to the anonymous array.

      $array[2][3] gets the 4th element of the array referenced by the 2nd element of @array. perllol

      All together: 

      my @recs;
while (read($fh, my $rec, 158)) {
    push @recs, [ unpack 'C*', substr($rec, 22, 13) ];
}

print $recs[2][3];

      [download]

      Since you're using unpack anyway, you can just skip over the unwanted bytes instead of using substr. 

          push @recs, [ unpack 'x22 C13', $rec ];

      [download]

      Update: Ooops, was missing the "*" in the unpack format.

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